"In my view the law is clear. If a man is injured in such a way that his leg may give way at any moment he must act reasonably and carefully. It is quite possible that in spite of all reasonable care his leg may give way in circumstances such that as a result he sustains further injury. Then that second injury was caused by his disability which in turn was caused by the defender's fault. But if the injured man acts unreasonably he cannot hold the defender liable for injury caused by his own unreasonable conduct. His unreasonable conduct is novus actus interveniens. The chain of causation has been broken and what follows must be regarded as caused by his own conduct and not by the defender's fault or the disability caused by it. Or one may say that unreasonable conduct of the pursuer and what follows from it is not the natural and probable result of the original fault of the defender or of the ensuing disability. I do not think that foreseeability comes into this. A defender is not liable for a consequence of a kind which is not foreseeable. But it does not follow that he is liable for every consequence which a reasonable man could foresee. What can be foreseen depends almost entirely on the facts of the case, and it is often easy to foresee unreasonable conduct or some other novus actus interveniens as being quite likely. But that does not mean that the defender must pay for damage caused by the novus actus. It only leads to trouble if one tries to graft on to the concept of foreseeability some rule of law to the effect that a wrongdoer is not bound to foresee something which in fact he could readily foresee as quite likely to happen. For it is not at all unlikely or unforeseeable that an active man who has suffered such a disability will take some quite unreasonable risk. But if he does he cannot hold the defender liable for the consequences. So in my view the question here is whether the second accident was caused by the appellant doing something unreasonable." [Bold added in this and other citations] 11. The difficulty with which this formulation presents trial courts is that "unreasonable" is a protean adjective. Its nuances run from irrationality to simple incaution or unwisdom. It is helpful to locate its correct position on the scale of meanings by recalling that its purpose in this context is to determine the point at which the law regards a consequence as too remote. 12. The account of remoteness on which Mr Nolan founds is that described by Lord Rodger in Simmons v British Steel plc[2004] UKHL 20 : "
"69. How, then does one identify a plaintiff's "true loss" in cases of tort? This question has generated a vast amount of legal literature. I take as my starting point the commonly accepted approach that the extent of a defendant's liability for the plaintiff's loss calls for a twofold inquiry: whether the wrongful conduct causally contributed to the loss and, if it did, what is the extent of the loss for which the defendant ought to be held liable. The first of these inquiries, widely undertaken as a simple "but for" test, is predominately a factual inquiry. The application of this test in cases of conversion is the matter now under consideration. I shall return to this in a moment. 70. The second inquiry, although this is not always openly acknowledged by the courts, involves a value judgment ("ought to be held liable"). Written large the second inquiry concerns the extent of the loss for which the defendant ought fairly or reasonably or justly to be held liable (the epithets are unchangeable). To adapt the language of Jane Stapleton in her article "
“39 In this case, the suggested novus actus interveniens that "breaks the chain of causation" so that Wincanton is not liable for the consequences of the second accident is the unreasonable conduct of the claimant, Mr Spencer. In the Scottish case of McKew v Holland & Hannen & Cubitts (Scotland) Ltd (1970) SC (HL) 20,[1969] 3 All ER 1621 , Lord Reid stated (at pages 25 and 1623 respectively) that "if the injured man acts unreasonably he cannot hold the defender liable for injury caused by his own unreasonable conduct. His unreasonable conduct is novus actus interveniens". 40 When Lord Reid considered the facts of that case he held that the chain of causation from the original tortious act of the defender was broken by a combination of two things. First, the pursuer's knowledge that his leg was likely to give way suddenly and without warning; and secondly, the pursuer's decision to start the descent of very steep stairs without a handrail, ahead of his adult family, with only his child to help him and not taking greater care in doing so. But Lord Reid also said that the pursuer's decision to try and jump when he realised he had lost his balance was no more than an error of judgment. That act was not, in itself, unreasonable conduct. 41 Lord Rodgers cites the McKew case in support of his second qualification in Simmons.As I have already noted, Lord Bingham quoted the whole summary of the Lord Rodgers' five points, including the citations, in Corr. 42 Lord Reid did not expand on what he meant by "unreasonable conduct". In the English case of Emeh v Kensington and Chelsea and Westminster Area Health Authority[1984] 3 All ER 1044 at 1049e, Waller LJ referred to Lord Reid's speech in McKew.Waller LJ quoted the passage where Lord Reid dealt with the argument about the effect of the pursuer's decision to jump when he started to lose his balance, which Lord Reid held was not unreasonable conduct. Waller LJ continued: "So the degree of unreasonable conduct which is required is, on Lord Reid's view, very high". 43 In the current and previous edition of Clerk & Lindsell on Torts(para 2-97 of the current edition), it is submitted that "for the claimant's subsequent conduct to be regarded as a novus actus interveniens it should be such as can be characterised as reckless or deliberate". Speaking for myself, I regard that as an unhelpful suggestion which is not warranted by any decision cited to us. Nor is it supported by the passage in the decision of Evans-Lombe J in Barings plc (in liquidation) v Coopers & Lybrand (a firm)[2003] EWHC 1319 (Ch) , which is cited in the footnote at the end of the sentence in Clerk & Lindsell that I have quoted. Indeed, Evans-Lombe J refers to the McKew case and others when considering the test for what may constitute a break in the chain of causation from a particular act of negligence. He says (citing a dictum of Roskill LJ in the Court of Appeal in Lambert v Lewis[1982] AC 225 at 252C) that the act need not necessarily be reckless. Evans-Lombe J states, correctly in my view, that "what will constitute such conduct is so fact-sensitive to the facts of any case where the issue arises that it is almost impossible to generalise". 44 I would accept that there is, inevitably, a degree of tension between: (a) certain conduct of a claimant such that the defendant whose liability for prior negligence is established is not responsible for the consequences of events following that conduct; and (b) certain conduct of a claimant which is such that the defendant remains responsible for those consequences, but his liability is reduced because the claimant is held to be contributorily negligent within the terms of theLaw Reform (Contributory Negligence) Act 1945 .After all, a claimant will only be held contributorily negligent under section 1(1) of 1945 Act if (a) he has been at "fault", i.e. he has not acted with reasonable care in the circumstances, and (b) that "fault" has had a causative effect on the injury or other damage. 45 The line between a set of facts which results in a finding of contributory negligence and a set of facts which results in a finding that the "unreasonable conduct" of the claimant constitutes a novus actus interveniens is not, in my view, capable of precise definition. The cases I have referred to have provided guidance. But, in my view, each case will depend on the facts and, in Lord Nicholls' phrase, the court will have to apply a value judgment to the facts as found.”